Covalent Bonding
Goal of the class
• To learn how covalent bonds are formed
between atoms
• Question of the day: What do Lewis dot
structures show?
• Previous Answer: Ionic bonds are formed
when one atom takes the electron(s) of
another atom and are then attracted.
Covalent Bonding
• Non metals combine together by sharing
electrons.
• The shared pair of electrons holds the two
atoms together.
– It's called a covalent bond.
• The group of atoms bonded together in this
way is called a molecule.
Examples of Covalent Molecules
• Hydrogen (H2)
• Water (H2O)
• Ammonia (NH3)
• Methane (CH4)
Properties
• Covalent compounds are usually gases or
liquids with low melting points or boiling
points.
• They don't conduct electricity.
Dot and Cross Diagrams
• Dot and cross models show how a pair of
electrons forms a covalent bond.
• Notice that in the diagrams only the electrons
in the outer shell of each atom are shown.
• All atoms want a full valence shell – octet rule
Dot and Cross Diagrams
Practice
• Draw a dot and cross diagram for water (H2O)
• Again for methane (CH4)
Lewis Dot Structures
• Lewis dot structures are an easy and helpful
way to diagram valence electrons
• The electrons must be arranged like this:
Be
C
O
Ne
Lewis Dot Structures
Double and Triple Bonds
• Some compounds are formed when two
elements share more than one electron with
each other.
• These form double or triple bonds
• Much stronger than single bonds
Questions
• Draw a Lewis dot diagram hydrogen
cyanide (HCN)
Vocabulary
• Covalent bonding – A type of chemical
bond where two atoms are connected to
each other by sharing pairs of electrons
• Octet – a group of eight things
Homework
• Please read Chemical Interactions
textbook pages 57-61
• Please complete Chemical Interactions
workbook page 18.